Technical Field
The present invention relates to an image forming system, an image forming device, a post-processing device, and a non-transitory computer readable recording medium stored with a conveyance abnormality detection program.
Background Art
In the image forming system, a technique referred to as automatic purging is known in which when a conveyance abnormality such as a jam or the like occurs in a paper conveyance path, the conveyance of the paper is stopped, and after the paper which has caused the jam is removed, the paper remaining in the conveyance path is automatically ejected. By virtue of the automatic purging being performed, it is possible to decrease a load for the user to process the jam such as operation for removing the paper remaining.
However, due to the high functionality of the image forming system and the extension of the conveyance path, a jam can occur again when the paper is conveyed by automatic purging.
A technique is known for detecting a jam while the paper is being conveyed by automatic purging (for example, Japanese Patent Publication Laid-open No. 1995-301963).
As the method for detecting a jam, a method is known such that the time from when one sensor provided on the conveyance path detects the leading end of the paper to when it detects the trailing end of the paper is calculated as the paper passing time, and when the paper passing time exceeds a predetermined threshold value, it is detected as a jam.
However, in the technique described in the above patent document, a jam is detected on the assumption that the papers are conveyed sheet by sheet during automatic purging. Therefore, no attention is paid to a case where the papers are conveyed while overlapping each other during automatic purging.
For example, upon occurrence of a jam, the respective devices configuring the image forming system notify the occurrence of the jam, an instruction to stop the paper conveyance or the like to each other via communication. Due to a time lag associated with this communication or the like, the timing that the paper conveyance is stopped differs from device to device. Thus, it sometimes happens that the preceding downstream-side paper is caught up by the succeeding upstream-side paper so that the papers are stopped in a state of partially overlapping each other.
In this manner, when the papers are conveyed in a state of overlapping each other by automatic purging without changing the state, there is no interval between the papers so that the time from when one sensor detects the leading end of a downstream-side paper to when it detects the trailing end of an upstream-side paper is detected as the paper passing time. For example, when a jam is detected based on the length of the paper passing time, the paper passing time is increased because of the papers being conveyed while overlapping each other so that there is a possibility that despite the papers being conveyed, it is erroneously determined that a jam has occurred.